Traffic traversing communication networks is sometimes subject to network congestion. Various techniques for detecting and controlling congestion are known in the art.
For example, Ramakrishnan et al. describe congestion control techniques that use Explicit Congestion Notification (ECN), in Request for Comments (RFC) 3168 of the Internet Engineering Task Force (IETF), entitled “The Addition of Explicit Congestion Notification (ECN) to IP,” September, 2001, which is incorporated herein by reference.
Another congestion notification scheme, referred to as Quantized Congestion Notification (QCN), is specified in “IEEE P802.1Qau/D2.4—Draft Standard for Local and Metropolitan Area Networks—Virtual Bridged Local Area Networks—Amendment: Congestion Notification,” Oct. 28, 2009, which is incorporated herein by reference. In the QCN scheme, bridges detect the congestion state of specified output queues, and send congestion notification messages to the sources of a sampling of the frames in the queue.